Method for producing helical seam welded steel pipe

ABSTRACT

In the formation of helical seam welded steel pipe from strip material, variations in the strip material are recorded and compared with nominal values and, based on the differences between the actual and nominal values, the helical bending of the strip material is controlled to maintain the spring back force of the material within permissible limits.

' United States Patent Gross et al. I Dec. 3, 1974 METHOD FOR PRODUCING HELICAL [56] References Cited SEAM WELDED STEEL PIPE UNITED STATES PATENTS [76] Inventors: Heinz Gross, Reichsmarkstrasse 1,884,658 10/1932 Gladkov et al. 228/17 142, 4600 Dortmund-sybu g, 3,775,835 12/1973 Cauffiel 29/4773 Germany; Harry C. Wade, 1205 Fennel St E N 104, H il Primary ExaminerAndrew R. .luhasz Ontario; John W, Win 20 Da d Attorney, Agent, or FirmToren, McGeady and Dr., Fonthill, Ontario, both of Stanger Canada 22 Filed: Apr. 30, 1973 [57] ABSTRACT In the format1on of helical seam welded steel pipe p 355,663 from strip material, variations in the strip material are recorded and compared with nominal values and, [30] Foreign Application Priority Data based on the differences between the actnal and nomi- M 4 972 0 man 2221776 nal values, the hellcal bendlng of the strip material 1s ay y controlled to maintain the spring back force of the 52 us. 01 29/477.3, 29/488, 72/17, materal permssble 219/62, 228/9 51 Int. Cl B23k 31/02 2 Clams 3 Drawmg Flgures [58] Field of Search 29/477, 477.3, 488; 228/8,

PATENTEL BEE 31974 SHEU 1 BF 2 METHOD FOR PRODUCING HELICAL SEAM WELDED STEEL PIPE SUMMARY OF THE INVENTION The present invention is directed to the formation of helical seam welded steel pipes and, more particularly, it involves checking the deformation resistance of the strip material used in forming the pipe and adjusting the helical bending of the pipe in accordance with the variations in deformation resistance.

Helical seam welded steel pipe is produced, as is known, from hot wide strip material, available in coil form or in flat form. Initially, if it is necessary to do so after uncoiling the strip material, it is straightened, and then the edges are cut in the proper form for the welding process. In place of relatively thin wide strip material, it is also possible to use long heavy plates which have not been coiled,.for forming the pipe. The preheated wide strip material or heavy plate material, which for simplicitys sake will be called plate strip, is fed by means of a driving unit over guide systems and an edge bending machine to a pipe shaping machine which continuously deforms the plate strip into a cylindrical helical seam pipe body. The edge bending machine through which the plate strip is conducted, takes into account the roofing-over, frequently called the "bamboo effect" in the industry, in the range of the welded seams, which effect usually appears during the manufacture of helical seam pipes. Such edge bending machines are known.

In producing the welded pipe, the helical seam pipe body is supported either by rollers acting on its outer circumference, a socalled roller cage, or by rollers acting on its inner circumference, a so-called roller star. The pipe shaping machine consists, for. example, of a three-roll bending machine, which consists of a threepoint bending system or of athree roll bending device and an additional bending roll, which willbe more fully described below. The deformation of the plate strip in the pipe shaping machine is effected primarily in the plastic state, and, unavoidably, also in the elastic state. To feed the deformed plate strip to the unwelded helical seam pipe body on the rollers of the roller cage or roller star, the pipe body should not completely relax so that a small amount of elastic deformation is maintained. A helical seam pipe body split in the longitudinal direction has a resilience which is characterized as spring back" in the industry. Further, a distinction is made between positive spring back and negative spring back. Due to variations in the plate strip thickness caused by rolling and also by variations in other material properties, adequate pipe diameter tolerances, but different spring back forces are obtained with constant geometric adjustment of the bending rolls of the pipe shaping machine and of the roller cage.

Since for various reasons all geometric and mechanical values of the pipe strip can be guaranteed only within predetermined tolerances for the application of the pipe,.it is necessary to maintain the spring back of helical pipe bodies split in the longitudinal direction within desired given limits.

Therefore, the present invention is directed to the problem of forming helical seam welded pipe by taking into account the fluctuations in the properties of the platestrip used for the pipe body so that the undesired effects of such fluctuations can be avoided.

In accordance with the present invention, the deformation resistance of the plate strip material is measured before it enters the strip bending machine and the measured value is compared with a nominal value for providing a control on the operation of the strip bending machine so that an adjustment can be provided whereby the curvature of the strip material is retained within permissible limits with regard to spring back, despite fluctuations of the properties of the strip material. Naturally, the control of the strip bending machine requires a knowledge of the extent to which variations in the deformation resistance of the strip material affect the pipe to be produced. Such information can be obtained, however, by making certain tests before commencing production of the pipe. In such tests, samples in the form of a ring are cut from welded test pipes, and the rings are cut up lengthwise and the positive or negative spring back is measured. From the test information obtained, it is possible to determine the relationship between spring-back, deformation resistance and the curvature produced in the strip bending machine. From a test series the results of which can be recorded in graphs or tables, it is possible to determine the manner in which the controlmust be set quantitatively for automatically adjusting the strip bending machine based on fluctuations in the properties of the strip material for producing a pipe whose spring back characteristic remains within permissible limits.

By varying the relative geometric arrangement of the bending rolls of the three-roll bending machine, it is possible to obtain different deformation radii of the strip. However, the requirement for maintaining the spring back of the helical seam pipe within permissible limits cannot always be achieved with the required accuracy. Even a minor variation in the adjustment of the three-roll bending machine during the formation of the helical seam pipe produces, as a result, different diameters and violates other control relations required for the pipe production.

Accordingly, to overcome this disadvantage, the present invention utilizes a strip bending machine in the form of a three-roll bending machine with an additional roll connected to it so that the roll moves transversely of the direction of the movement of the strip as it passes into the machine and the roll controls the entrance angle of the strip in the vertical plane as it enters the machine. The operation of the roll is determined by checking the deformation resistance of the strip upstream from the position at which it enters the bending machine.

In another embodiment of the invention, the pressures developed in the above-mentioned edge bending device are used, as mentioned above, as the actual values, because all quantitative fluctuations in the plate strip material properties, which influence the deformation resistance, result in a variation of the pressures which are developed in the edge bending device.

The various features of novelty which characterize I the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing: a

FIG. 1 is a schematic showing, in elevation, of a plant for the production of helical seam welded pipes;

FIG. 2 is a cross sectional view taken along the line Il-II in FIG. 1; and

FIG. 3 is an enlarged detail of a portion of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION ,As shown in FIG. 1, plate strip material 1 to be used in forming helical seam welded pipe is straightened in a straightening machine 2 and then passes through an edge trimmer 3 which forms its edges in the proper configuration for the welding operation. Downstream from the edge trimmer, the strip material passes through a main driver stand 4 which effects the feed of the plate strip material through the plant for producing the helical seam welded pipe, and the edges of the strip material are bent, based on the so-called bamboo effeet, to compensate for this undesired effect which appears in the finished helical seam pipe. From the main driver stand 4, the plate strip material 1 passes through a bending roll stand 5 and is directed into a pipe bending or shaping machine consisting of the bending rolls 6, 7 and 8. Within this shaping machine the plate strip material is bent to a radius which ensures that its outer surface bears against the rollers of a roller cage 9. The bearing of the curved plate strip on the rollers is achieved only to a minor extent by elastic deformation of the plate strip developed in the shaping machine and almost exclusively by permanent deformation which exceeds the elastic limit. In the embodiment illustrated, the bending rolls 6 located below the. strip material and the bending rolls 7 positioned above the strip material are set or fixed so they do not change position during operation, however, the bending roll 8 is displaceable transversely of the direction in which the strip enters the bending machine. The bending stand 5 consists of the bending rollers 51, 52, 53 and 54 represented schematically in FIG. 2. Each pair of the bending rollers 51, 52 and 53, 54 is provided in its support with an inductive pressure cell 12 which transforms pressure increases and decreases developed between the bending rollers which are proportional to the variations in the properties of the plate strip material, into electrical impulses. The electrical impulses are transmitted over an amplifier 13 to a difference-former 14. The results plotted in the testing series, representing nominal values, are stored in the setting means 15. The setting means is inter-connected with the difference-former 14.

In this set-up, any instantaneous deviation in the properties of the plate strip material I is compared in the difference-former 14 with the nominal values from the setting means 15 and, as a result, any deviation tarding element 16 stores the received electrical impulse until the section of the plate strip material which generated the impulse reaches the bending roll 8 at which moment the stored signal is released. The electrical impulse is amplified within amplifier l7 and is fed to an electromotor drive 18 which adjusts the bending roll in the vertical direction over a lever gear represented schematically in FIG. 1. The vertical adjustment of the bending roll, that is in the direction transverse to the movement of the strip material into the bending machine, has a prebending effect on the plate strip material before it passes through the radially fixed bending rolls 6 and 7.

Therefore, since the prebending effect is timed to correspond exactly with the section of the plate strip material which generatedthe signal, the spring back, which is a function of the residual stresses in the pipe cross section, can be kept within permissible limits.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Method of producinghelical seam welded pipe from strip material comprising the steps of bending the strip material into a helical form by plastic deformation and welding the oppositely disposed juxtaposed edges of the strip material togethenwherein the improvement comprises, prior to bending the strip into helical form, continuously measuring the deformation resistance of the strip, and adjusting the bending operation in accordance with the measured deformation resistance so that the spring back of the strip material remains within permissible limits regardless of the variations in the strip material properties along its length.

2. Method, as set forth in claim 1, wherein the steps of measuring the deformation resistance and adjusting the bending operation includes continuously registerfrom the nominal value is transformed into an electrical impulse which is fed to a retarding element 16. The reing increases and decreases in the pressure of the strip material significant of the deformation resistance at a station located upstream from the location of the bending operation, converting the pressure differencesinto electrical impulses, collecting the pressure differences represented as electrical impulses and comparing them with nominal values for the strip material, storing the collected information until the section of the strip material which supplied the information reaches the helical bending station and transforming the collected information for adjusting the bending operation in accordance with the collected information for retaining the spring back of the strip material within permissible lim- Its. 

1. Method of producing helical seam welded pipe from strip material comprising the steps of bending the strip material into a helical form by plastic deformation and welding the oppositely disposed juxtaposed edges of the strip material together, wherein the improvement comprises, prior to bending the strip into helical form, continuously measuring the deformation resistance of the strip, and adjusting the bending operation in accordance with the measured deformation resistance so that the spring back of the strip material remains within permissible limits regardless of the variations in the strip material properties along its length.
 2. Method, as set forth in claim 1, wherein the steps of measuring the deformation resistance and adjusting the bending operation includes continuously registering increases and decreases in the pressure of the strip material significant of the deformation resistance at a station located upstream from the location of the bending operation, converting the pressure differences into electrical impulses, collecting the pressure differences represented as electrical impulses and comparing them with nominal values for the strip material, storing the collected information until the section of the strip material which supplied the information reaches the helical bending station and transforming the collected information for adjusting the bending operation in accordance with the collected information for retaining the spring back of the strip material within permissible limits. 